Response of Nitrogen Use Efficiency to Plant Density and Nitrogen Application Rate for Maize Hybrids from Different Eras in Heilongjiang Province

Abstract

In this study, eight typical maize hybrids released from 1970s to 2000s in Heilongjiang Province were selected to investigate the responses of grain yield, nitrogen (N) partial factor productivity (PFP), N agronomic efficiency (NAE) and N recovery efficiency (NRE) to N application rate and plant density in 2009 and 2010. During the variety improvement period of 1970s–2000s, PFP and NRE increased significantly by 3.41 kg kg–110 yr–1and 2.26 percent 10 yr–1, respectively. NAE increased significantly from 1970 to 1990 and descended after 1990. N harvest index decreased significantly by 1.51 per cent 10 yr–1. Grain N, stem N and leaf N accumulations rose significantly by 0.09, 0.07, and 0.12 g plant–110 yr–1. There were significant interactions among eras, plant densities and N application rates for above indicators. Nitrogen use efficiency exhibited decline trends with increasing N application rate and parabolic shape response to increasing plant density, and got the maximum in the population range of 50 000–70 000 plants ha–1. The theoretical optimal plant density for the maximal NUE was higher in newer hybrids than in the older ones. Higher plant population led to decrease N accumulation and N harvest index in grain, stem and leaf for all hybrids from different eras. Higher N application rate tended to promote N accumulation in grain, stem and leaf, but had different effects on N harvest index for hybrids from different eras. Compared to the varieties released abroad, there is a great potential in maize variety improvement for high-yield and high-NUE in Northeast China. According to the existing variety’s traits, increasing plant density can enhance not only maize yield but also NUE.